1. Field of the Invention
Embodiments of the present invention generally relate to a method of forming a damascene structure and a computer program executable to perform the method.
2. Description of the Related Art
In forming a damascene structure, previous methods have utilized a dual hard mask structure to open up the via and expose the conductive material at the bottom of the via. FIGS. 1A-1D illustrate a typical prior art process scheme. As seen in FIG. 1A, initially, a single etch stop layer 103 is formed over a dielectric layer 101 and a contact area 102. The etch stop layer 103 is about 1,000 Å thick. On top of the etch stop layer 103, another dielectric layer 104, a first hard mask 105, and a second hard mask 106 are formed.
The second hard mask 106 is then patterned. Once the second hard mask 106 is patterned, a sacrificial layer 107 is formed within and on top of the second hard mask 106. Then, a resist 108 is formed on top of the sacrificial layer 107 and is patterned to create a trench pattern 109. The resist 108 is about 1,000 Å thick. The patterned resist 108 is not aligned with the patterned second hard mask 106 (FIG. 1A).
A via pattern 110 as shown in FIG. 1B is then etched into the structure. The patterned resist 108 is removed as is the sacrificial layer 107 and a trench pattern 111 is formed (See FIG. 1B).
A portion of the first hard mask 105 is now exposed. A sacrificial layer 112 is then deposited within via pattern 110 on top of the etch stop layer 103 (see FIG. 1C). The exposed second hard mask 106 is now etched and removed as is a portion of the dielectric layer 104 and all of the sacrificial layer 112 so that a trench pattern 113 and a via pattern 114 are formed (see FIG. 1D).
FIG. 2A-2E show another process scheme of the prior art. As seen in FIG. 2A, initially, a single etch stop layer 203 is formed over a dielectric layer 201 and a contact area 202. On top of the etch stop layer 203, another dielectric layer 204, a first hard mask 205, and a second hard mask 206 are formed. The second hard mask 206 is then patterned through etching. Once the second hard mask 206 is patterned, a sacrificial layer 207 is formed within and on the patterned second hard mask 206. Then, a resist 208 is formed on top of the sacrificial layer 207 and is patterned to form a trench pattern 209. The resist 208 is about 1,500 to about 3,000 Å thick. The patterned resist 208 is not aligned with the patterned second hard mask 206 (FIG. 2A).
The patterned resist 208 is then removed as are the sacrificial layer 207 and the first hard mask 205 that was not covered by the patterned resist 208. Additionally, a portion of dielectric layer 204 is removed down to the etch stop layer 203 so that a via pattern 210 and a trench pattern 211 are formed (See FIG. 2B).
A portion of the first hard mask 205 is now exposed. A sacrificial layer 212 is then deposited within the via pattern 210 and on top of the etch stop layer 203 (see FIG. 2C). A hard mask 213 is formed on top of the sacrificial layer 212. A patterned resist 214 is formed on top of the hard mask 213 forming a trench pattern 215.
Using the patterned resist 214 as a mask, a trench pattern 216 is etched through the hard mask 213 and sacrificial layer 212 leaving the patterned hard mask portions 213A, 213B and sacrificial layer portions 212A-212C (see FIG. 2D). The via is then formed by etching. The sacrificial layer 212B, the hard mask portions 213A, 213B, and the sacrificial layer portions 212A-212C are all removed leaving a via pattern 217 and trench pattern 218 (FIG. 2E).
In each of the above described prior art methods, a sacrificial layer is deposited within the via pattern. The sacrificial layer within the via along the sidewalls of the dielectric layer is a problem. The sacrificial layer will interact with the dielectric layer and poison the structure. Additionally, the topmost hard mask layer is a metal containing hard mask. If the hard mask is not metal containing, then there will be corner chopping of the dielectric layer when the trench is etched. Corner chopping is when material is undesirably removed from a corner of a layer. A metal containing hard mask is more resistant to etching than a dielectric layer. Therefore, the metal containing hard mask will protect the underlying dielectric layers from etching at the corner when forming the trench. There is a drawback to using a metal containing hard mask. In order to remove a metal containing hard mask, an aggressive etchant must be used that can easily damage the damascene structure. In addition to the metal etching, CMP must also be used. Also, the bottom etch stop layer must be thick enough (about 1000 Å) in order to effectively form the via. An etch stop layer that is too thick becomes a problem because of the increased capacitance.
Therefore, there is a need in the art to provide an effective method of forming a damascene structure that solves the problems mentioned above.